In the prior art, delta robots have proven their worth in particular for the highly dynamic handling of relatively lightweight objects—such as the packaging of foods in small amounts or medication—since they permit extremely high dynamics of up to three packaging operations per second.
The first delta robots comprised three upper arms. However, variants with four and more upper arms are known.
In each case, three and in some cases four elongate upper arms are mounted so as to be pivotable about an axle in each case. At the free ends thereof, two mutually parallel rods are pivotably mount, which in turn are in pivotable connection with the parallel plate. By a swivelling of the servo drives, the parallel plate can be maneuvered into any desired position of the intended work space. Because the lower arms consist of two parallel rods, the parallel plate thus always moves—as its name suggests—parallel to the base plate.
In the prior art, most delta robots consist of a base plate on which three servo drives are mounted. For applications in hygienically critical areas, such as the production of foods, pharmaceuticals or electronic devices, the base plate is extended within a housing so that lubricants and any abrasion debris from the drives and/or the transmission cannot detach and fall into the product.
In the prior art, the U.S. Pat. No. 6,577,093, Hvittfeldt, discloses a delta robot for hygienic requirements, in which all drives are disposed within a housing. It is thereby avoided that lubricants or abrasion debris from the bearings of the motor and drive escape and thereby contaminate an otherwise hygienic environment. A further, very important advantage is that the housing can also be made of a material that can withstand the very corrosive cleaning agents for equipment in food processing.
However U.S. Pat. No. 6,577,093 disadvantageously gives no indication how it is ensured that the areas of the robot outside the housing, that is to say the arms and the joints of the robot, do not emit contamination during operation and in the event of collisions.
Similarly, there are no indications of how the arms and joints can be adapted to the requirement for maximum dynamics. As is known, a high obtainable cycle rate is always the reason why the principle of a delta robot is chosen at all. For slow movements, simple linear handling may be more suitable. The requirement for high dynamics is thus already implied in the choice of a delta robot.
Despite the stated object of satisfying hygienic requirements, that is to say withstanding the effects of the most aggressive cleaning agents, proposals to this end are lacking. The consequences of a collision are also not discussed.
However, it is quite clear that, for robots with extremely high dynamics, elements of the lowest weight possible are to be preferred in general, specifically the greater their effective movement radius, since the moment of inertia of each mass for movement about the centre of a circle is known to increase with the fourth power of the radius.
From this point of view, the delicate and therefore lightweight universal joint or cardan joint is in principle interesting for connection to the arms and to the parallel plate of a delta robot. The maximum pivoting angles that can thereby be achieved, however, are significantly lower in comparison to a ball joint, consisting of a ball head and a complementary ball socket sliding thereon. Because ball joints thus have a larger pivot angle and thereby permit a larger working space, they are now the joint design most used for delta robots.
In the prior art, U.S. Pat. No. 5,333,514, Toyama, discloses a delta robot, the arms and parallel plate of which are connected together via ball joints.